Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a positive electrode active material and negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can-type secondary battery where the electrode assembly is included in a metal can and a pouch-type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and power storages. When being used for middle-sized or large-sized devices, a great number of secondary batteries are electrically connected to enhance capacity and output. In particular, in middle-sized or large-sized devices, pouch-type secondary batteries are frequently used since they can be easily stacked and have light weight.
Generally, in order to ensure cooling performance, various cooling methods such as direct or indirect water or air cooling are applied to a battery pack. In particular, in case of an existing battery pack, in order to remove heat emitted during a charging or discharging process, a plurality of cooling members made of metal material is disposed around a secondary battery, and a cooling medium such as air or water is supplied around the cooling member. For example, in an existing technique, in many cases, a metallic cooling member such as a cell cover or a cooling plate for the flow or thermal conduction of the cooling medium is interposed between secondary batteries.
However, in order to additionally provide such a cooling member near a plurality of secondary batteries or prepare a channel space for the flow of a cooling medium, the battery pack inevitably has an increased volume as a whole and also has a complicated structure. Therefore, the battery pack has deteriorated efficiency in fabrication, also has a limit in miniaturization, and also has an increased fabrication time and cost.
In addition, in an existing battery pack, a separate device such as fans or pumps is used for circulating the cooling medium, but this may increase fabrication time and costs and a volume of the battery pack, and the battery pack may have more complicated structure.
Further, if a cooling member made of electrically-conductive metal like an aluminum metal, insulation should be ensured between the cooling member and the secondary battery. Therefore, the battery pack may have more complicated structure due to a configuration for the insulation, and its volume and cost may also be increased.